This invention relates generally to magnetic storage media, and more particularly to magnetic tape cartridges incorporating a non-volatile memory.
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the software and data as described below and in the drawings hereto: Copyright(copyright) 2000, Sony Electronics, Inc., All Rights Reserved.
Magnetic tapes are sequential storage media capable of efficiently and reliably storing large amounts of data. Because of their large storage capacity and relatively low cost, magnetic tapes are commonly used for data backup. A backup server in a network can utilize one or more magnetic tape drives to automatically backup files stored on user computers connected to the network. Magnetic tapes are also used for storage management, multimedia storage and retrieval, real-time data acquisition, and transporting large amounts of data.
Although magnetic tapes offer the aforementioned advantages, they are relatively slow compared with other mass storage devices such as hard disks. Consequently, efforts have been made to decrease access time to data stored on a magnetic tape. One method of increasing the speed of data access involves incorporating a non-volatile memory into the magnetic tape cartridge. System log information may be stored in the non-volatile memory, enabling a tape drive to quickly locate and access a data file stored in a particular partition along the magnetic tape.
A magnetic tape incorporating a non-volatile memory may be formatted to include a series of partitions. One or more data files may be stored within a data area in a particular partition. A user may wish to delete a data file stored on the magnetic tape. There are a variety of possible methods of deleting data on a magnetic tape. One method, which is the most commonly used method of erasing data from a magnetic tape, is to simply overwrite the original data with new data. An end-of-data (EOD) marker is recorded after the new data that indicates where the tape drive stopped overwriting the original data.
A user may accidentally overwrite original data in an overwrite operation. The original data that was written over typically is lost and cannot be recovered. However, some of the original data may still exist past the EOD marker marking the end of the new data. By reading past an EOD marker, a user can recover original data past the EOD marker that was not overwritten. In the past, customized firmware was used to enable a user to read past the EOD marker. However, using customized firmware is costly, inconvenient, and time consuming because the tape drive must be updated with the new firmware.
A method and apparatus to read past an EOD marker on a magnetic tape is described herein. In one embodiment, a data storage device includes a casing, a pair of spools enclosed within the casing, a magnetic tape coiled around and extending between the spools, and a read-past-EOD marker flag stored in the data storage device. The read-past EOD marker flag may be located in a non-volatile memory coupled to the data storage device.
Additional features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.